For improved frictional coupling of two members or for sliding bearing (antifriction) purposes, it is known to provide a bonded composite which comprises a supporting metal layer and a facing layer of fiber-reinforced synthetic resin, the latter defining the sliding (friction or antifriction) characteristics of the material.
In German Pat. No. 30 16 041, for example, a bonded composite of the type described whose conventional or facing layer is an organic friction material utilizing a matrix of a phenol-formaldehyde resin which contains 15 to 50% by volume of comminuted carbon fibers with a mean length of 0.2 to 10 mm and a mean diameter of 3 to 50 microns, 7 to 20% by volume steel fibers and 10 to 15% by volume of a filler, generally a particulate solid. Friction layers composed of such friction material suffer premature fatigue under dynamic loading which will vary depending upon the type of synthetic resin matrix and may be traceable at least in part to the inclusion of steel fibers in the synthetic resin matrix.
In German patent publication (open application) No. DE-OS 29 35 205, a layered composite and a method of making it are described in which the synthetic resin matrix has good sliding characteristics and thus forms a highly desirable function layer which also contains short carbon fibers together with practically endless carbon fibers, i.e. carbon fibers of considerable length. The fabrication method described in this publication is complicated and extensive, inter alia, because of the requirement to provide adjacent fiber bundles and because of the means for introducing them and orienting them.
Furthermore, when the system of this publication is used to produce finished products such as journal bushings or sleeves bearing shells and the like, significant variations in quality are recognized. Apparently, when such materials are cut to permit the fabrication of the finished products, the long fibers suffer from shear breakage. Such shear breakage can be discerned upon stamping or other subdidivion of the blanks from sheet or strip workpieces. The fiber fragments upon such breakage appear to project from edges of the blanks and interfere with the ability to effectively use the materials.